Refactoring Legacy Code

Refactoring Legacy Code
By:
Adam Culp
Twitter: @adamculp
https://joind.in/talk/a3ecc

2
●
About me
– PHP 5.3 Certified
– Consultant at Zend Technologies
– Zend Certification Advisory Board
– Organizer SoFloPHP (South Florida)
– Organized SunshinePHP (Miami)
– Long distance (ultra) runner
– Judo Black Belt Instructor

3
●
Fan of iteration
– Pretty much everything requires iteration to do well:
● Long distance running
●
Judo
●
Development
●
Evading project managers
●
Refactoring!

6
●
Modernizing
– “Modernizing Legacy Applications in PHP” on LeanPub – by Paul M. Jones
– http://mlaphp.com

7
●
What is “Legacy Code”
– Is there a coding standard for your project?

8
●
– Is code using OOP?

9
●
– Is Composer used in your project?

10
●
– Is the project using a framework?

11
●
– Are you unit testing?

12
●
– Does your project avoid NIH?

13
●
– Does your project avoid NIH?
If you can answer “No” to any of these,
you may be creating “Legacy Code”!!!

14
●
What is “refactoring”?
– “...process of changing a computer program's source code without
modifying its external functional behavior...” en.wikipedia.org/wiki/Refactoring
– No functionality added
– Code quality

15
●
Two hats
– Adding Functionality Hat
– Refactoring Hat
– We add functionality, then refactor, then add more functionality ...

16
●
Then optimize
– Do not optimize while refactoring.
– Separate step.
– Refactoring is NOT optimizing.

17
●
Source Control
– Refactor in branch
– Allows rollback

18
●
Editor/IDE
– Makes searching easier
– Search within project

19
●
Style Guide
– Framework Interop Group
●
http://php-fig.org
●
PSR
– Faster reading
– United team

20
●
Testing
– Consistent results
– Prevents breaks
– Speeds up development

21
●
Modernizing Steps
– Autoloading
– Consolidate Classes
– Cleanup Globals
– Replace “new” (instantiation)
– Create Tests
– Extract SQL
– Extract Logic
– Replace Remaining “Includes”

22
●
Autoloading
– Namespaces
– PSR-0
●
Legacy code typically used long class names
– Usage = My_Long_Class_Name
– Translates to “/My/Long/Class/Name.php”
– Class = My_Long_Class_Name
●
If not, then PSR-4
– Use MyGreatNamespaceName
– Translates to /My/Great/Namespace/Name.php
– Class = Name

23
●
Autoloading Approaches
– Approaches
●
Global function
●
Closure
●
Static or Instance Method (preferred, if possible)
●
__autoload() - PHP v 5.0
– Need a central place for classes

24
●
Consolidate Classes
– Move to one location
●
Could be named “includes”, “classes”, “src”, “lib”, etc.

25
●
Consolidate Classes Step 1
– Search for include statements
●
(include, include_once, require, require_once)

26
●

27
●
– User class is now autoloaded, no more require_once.

28
●
Consolidate Classes Repeat
– Search for more instances

29
●
Cleanup “Global” Dependencies Steps
1 Search for global reference
2 Move global calls to constructor
3 Convert global call to a constructor parameter
4 Update global call to a class
5 Instantiate new class and pass as parameter (DI)
6 Repeat

30
●
Global Cleanup Step 1
– Search for global reference

31
●
Global Cleanup Step 2 & 3
– Move global call to constructor
– Pass values as properties

32
●
– Convert call to a constructor parameter

33
●
– Instantiate new class
– Inject as parameter (DI)

34
●
Global Cleanup Repeat
– Look for more instances to clean up

35
●
Steps to Replacing “new”
1 Search for “new”
2 Extract instantiation to constructor parameter. (if one time)
●
Or extract block of creation code to new Factory class. (if repeated)
3 Update instantiation calls
4 Repeat

36
●
Replacing “new” Step 1 (Single)
– Before

37
●
Replacing “new” Step 2 (Single)
– Inject Db object into class constructor. (DI)
– No longer instantiating within class

38
●
Replacing “new” (Multiple)

39
●
Replacing “new” Step 3 (Multiple)
– Create factory
– Extract “new” call to new factory

40
●
– Update instantiation calls

41
●
– Call to factory

42
●
Replacing “new” Repeat

43
●
Write Tests
– Code is fairly clean
– Write tests for entire application
– If not testable, refactor
●
Extract method
●
Replace temp with query
●
Etc.

44
●
Extract SQL
1 Search for SQL
2 Move statement and relevant logic to Gateway class
3 Create test for new class
4 Alter code to use new method
5 Repeat

45
●
Extract Logic
1 Search for uses of Gateway class outside of Transaction classes
2 Extract logic to Transaction classes
3 Test
4 Write new tests where needed
5 Repeat

46
●
Replace “includes”
– Search for left over includes
– If in current class
1 Copy contents into file directly
2 Refactor for: no globals, no 'new', DI, return instead of output, no includes
– More often
1 Copy contents of include as-is to new class method
2 Replace with in-line instantiation
3 Search for other uses of same, and update them as well
4 Delete original include file, regression test
– Test, create new tests if needed
– Repeat

47
●
Additional Possibilities
– Can now implement framework
– Leverage services
– Leverage events
– Use Composer

48
●
Why refactor
– Less bugs
– Faster development
– More stable
– Easier onboarding
– Save $$$

49
●
When/How to refactor
– Ask boss for time
– “Leave it cleaner than you found it”
– Do it on your own, it makes YOUR life easier

50
●
Challenges
– Manager Buy In
– Technical Challenge
– Social Challenge

51
●
Convince the boss
– Three kinds of managers:
●
Tech Savvy
●
Quality Centric
●
Time Driven
Right...

52
●
Tech Savvy boss
– Lower cyclomatic complexity
– SOLID
– Separation of concerns
– MVC/Framework
– Less bugs
– Easier onboarding

53
●
Quality Centric boss
– Code quality
– Tests
– Happier customers
– Less bugs

54
●
Time driven boss
– Faster feature delivery
– Higher productivity - less time reading
– Faster onboarding
– Less testing time
– Less debugging

55
●
Concluding Thoughts
– Do not refactor a broken application
– Have tests in place prior to refactor
●
Unit tests or
●
Functional tests or
●
Manual tests
– Do things in small steps
– Love iteration!

●
Thank you!
– Please rate at: https://joind.in/talk/a3ecc
Adam Culp
http://www.geekyboy.com
http://RunGeekRadio.com
Twitter @adamculp
Questions?

Refactoring Legacy Code

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (20)

Similar to Refactoring Legacy Code

Similar to Refactoring Legacy Code (20)

More from Adam Culp

More from Adam Culp (20)

Recently uploaded

Recently uploaded (20)

Refactoring Legacy Code